Two new trials of Ebola vaccines begin in Europe and Africa

LONDON (Reuters) - Two new Ebola vaccine trials began on Wednesday with volunteers in Britain, France and Senegal getting "prime-boost" immunizations developed by Bavarian Nordic, GlaxoSmithKline and Johnson & Johnson.

The mid-stage, or Phase II, trials are designed primarily to test the vaccines' safety, but will also assess whether they provoke an immune response against the deadly virus.

The development of the prime-boost and other vaccines was accelerated in response to vast outbreaks of Ebola in West Africa, where at least 11,200 people have died so far in Guinea, Sierra Leone and Liberia.

"The current Ebola outbreak has reinforced that speed of response is crucial," said Egeruan Babatunde Imoukhuede, who is coordinating one of the trials in Senegal.

"Outbreak diseases spread quickly, so any vaccination approach must be able to keep up."

Data from the World Health Organization show there were 30 confirmed cases of Ebola in West Africa in the week to July 5.

In Liberia, which had been declared Ebola-free in May, a sixth new case was confirmed on Tuesday in what health officials fear is a new wave of the outbreak.

While the number of Ebola cases has dropped sharply in recent months, researchers said the flare-up in Liberia underlines the need to push ahead with developing potential vaccines that may help control this and future outbreaks.

The trial of the Bavarian Nordic and J&J prime-boost combination initially aims to recruit more than 600 healthy adult volunteers in Britain and France.

Bavarian said it hoped to launch another later phase of this trial in Africa later this year involving 1,200 volunteers, but other large clinical trials have recently been thwarted by the drop in case numbers.

Previously planned trials of GSK, Merck and J&J shots in West Africa have been struggling to recruit volunteers with enough exposure to Ebola to prove whether their vaccines are doing the job and preventing infection.

The second trial will be conducted in Senegal and uses two vaccines tested first in people at Oxford University's Jenner Institute and being developed in a partnership with GSK. The first, based on a chimpanzee adenovirus, is designed to stimulate, or prime, an initial immune response, while the second is designed to boost that response.

Each vaccine is based on genetically modifying safe viruses to carry just one part of the Ebola virus that will stimulate the body's immune system. Researchers stressed that none of the shots contains any live Ebola virus.